The evidence for macroscopic life during the Palaeoproterozoic era (2.5–1.6 Gyr ago) is controversial1,2,3,4,5. Except for the nearly 2-Gyr–old coil-shaped fossil Grypania spiralis6,7, which may have been eukaryotic, evidence for morphological and taxonomic biodiversification of macroorganisms only occurs towards the beginning of the Mesoproterozoic era (1.6–1.0 Gyr)8. Here we report the discovery of centimetre-sized structures from the 2.1-Gyr-old black shales of the Palaeoproterozoic Francevillian B Formation in Gabon, which we interpret as highly organized and spatially discrete populations of colonial organisms. The structures are up to 12 cm in size and have characteristic shapes, with a simple but distinct ground pattern of flexible sheets and, usually, a permeating radial fabric. Geochemical analyses suggest that the sediments were deposited under an oxygenated water column. Carbon and sulphur isotopic data indicate that the structures were distinct biogenic objects, fossilized by pyritization early in the formation of the rock. The growth patterns deduced from the fossil morphologies suggest that the organisms showed cell-to-cell signalling and coordinated responses, as is commonly associated with multicellular organization9. The Gabon fossils, occurring after the 2.45–2.32-Gyr increase in atmospheric oxygen concentration10, may be seen as ancient representatives of multicellular life, which expanded so rapidly 1.5 Gyr later, in the Cambrian explosion.
We thank the Ministry of Mines, Oil, Energy and Hydraulic Resources and the General Direction of Mines and Geology of Gabon for collaboration and assistance, and the French Embassy at Libreville and the French Ministry for Foreign Affairs for support. We thank F. Mayaga-Mikolo, D. Beaufort, B. Cost, D. Thieblemont, F. Pambo and H. Sigmund for discussions. For assistance in Gabon and France, we acknowledge S. Accolas, T. Bonifait, B. Braconnier, N. Dauger, F. Duru, D. Fabry, F. Haessler, M. Jouve, G. Letort, D. Paquet, J.-C. Parneix, D. Proust, M. Stampanoni and X. Valentin. We also acknowledge the Institut Français du Pétrole, the Swiss Light Source (TOMCAT beamline) at the Paul Scherrer Institute, and the Centre de Microtomographie at the University of Poitiers (CdMT). Nordsim is operated under an agreement of the Joint Committee of the Nordic Research Councils for Natural Sciences (NOS-N), with further funding from the Knut and Alice Wallenberg Foundation; this is Nordsim contribution 256. Research was supported by the French CNRS-INSU, the Bureau de Recherches Géologiques et Minières (BRGM), the Danish National Research Foundation and the Swedish Research Council.
This file contains an animation of G-FB2-f mst1.1 microtomographic reconstruction showing inner structures through transparency.
This file contains an animation of G-FB2-f mst2.1 microtomographic reconstruction showing inner structures through transparency.
This file contains an animation of G-FB2-f mst3.1 microtomographic reconstruction showing inner structures through transparency.
This file contains an animation of G-FB2-f mst4.1 microtomographic reconstruction showing inner structures through transparency.